Clinical Experience With RIST-Based Multimodality Therapy in Relapsed Ewing Sarcoma: A Descriptive Single-center Case Series

Background: Outcomes for relapsed Ewing sarcoma remain poor. The RIST regimen (rapamycin, irinotecan, dasatinib, temozolomide) provides a targeted biological alternative to standard salvage chemotherapy. Methods: We report 3 patients treated with RIST for relapsed Ewing sarcoma. Results: One patient with measurable disease achieved an early partial response before progressing at 9 months. Two patients received RIST as post–local-therapy consolidation with no evidence of disease, maintaining disease control for 41 and 44 months. Toxicities were manageable and primarily hematologic, without treatment discontinuations. Conclusion: Prolonged outpatient RIST administration is feasible, and its role as multimodality consolidation warrants further prospective evaluation.